Programmable mouse like a G9, higher sensitivity when you're in tight quarters, low sensitivity when you're at medium to long range.
can't work that? keep setting your sensitivity lower and lower until you start cursing that you can't turn fast enough, then bump it back up.
Generally your sensitivity should be the width of your mouse on your mousepad, doing a 360 ingame, at least that's what someone said to me once, but from there i think i adjusted to what felt natural. But for sure you don't want a high dpi, and if you'er standing still not moving your mouse, your screen shouldnt be shaking all over the place. And to practice, always aim for the head. Don't spray out of laziness or what works, if you want to improve.